From e1663eeae46b3765a4e369e1fe70f1c1ef03cb0b Mon Sep 17 00:00:00 2001
From: Chirantan Ekbote <chirantan@chromium.org>
Date: Fri, 3 Sep 2021 18:31:25 +0900
Subject: [PATCH] Only change uid/gid when it's not 0

Only change the device uid/gid in the sandbox when it is not 0.
Otherwise, running crosvm as root makes minijail complain:

   libminijail[16370]: useless change to uid 0

BUG=none
TEST=run crosvm as root

Change-Id: Ida4b0e772ed000d3e42f77012af9d2505f64d92a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3141297
Auto-Submit: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Fergus Dall <sidereal@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
---
 src/linux.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/linux.rs b/src/linux.rs
index 03f4a91dbe..cd10673c53 100644
--- a/src/linux.rs
+++ b/src/linux.rs
@@ -1692,8 +1692,12 @@ fn add_current_user_to_jail(jail: &mut Minijail) -> Result<Ids> {
     jail.gidmap(&format!("{0} {0} 1", crosvm_gid))
         .map_err(Error::SettingGidMap)?;
 
-    jail.change_uid(crosvm_uid);
-    jail.change_gid(crosvm_gid);
+    if crosvm_uid != 0 {
+        jail.change_uid(crosvm_uid);
+    }
+    if crosvm_gid != 0 {
+        jail.change_gid(crosvm_gid);
+    }
 
     Ok(Ids {
         uid: crosvm_uid,